This invention relates to a suture needle having cutting edges and also to a method of producing such a suture needle.
There are well known suture needles whose distal end portion has a triangular, trapezoidal or rhombic cross-section, and has one or two cutting edges. Such various suture needles are used in accordance with the purpose of the surgical operation.
In order that the suture needle can have a good penetrating ability, the distal or foremost end thereof must be pointed. In a suture needle having a triangular cross-section as disclosed in Japanese Patent Publication No. 26783/89, its distal end portion is ground to form three ground surfaces so as to decrease the cross-sectional area of the distal end portion progressively toward the distal end of the suture needle. In this case, the foremost end of the suture needle is naturally pointed.
In a suture needle whose distal end portion has a quadrangular cross-section, when the distal end portion is to be ground to form four ground surfaces so as to decrease its cross-sectional area, the foremost end of the suture needle can be pointed only by precisely controlling the amount of grinding of each ground surface. For example, in a suture needle having a rhombic cross-section and having a pair of cutting edges, as disclosed in U.S. Pat. Nos. 1,506,262 and 3,238,942, the foremost end of the suture needle can be pointed when the amounts of grinding of the four ground surfaces are the same, and the pair of cutting edges intersect each other at this point. Otherwise, instead of such a pointed end, a short edge generally perpendicularly intersecting the longitudinal axis of the distal end portion is formed, and this edge intersects the cutting edges at its opposite end. In this case, the penetrating ability is worsened. Further, since the difference between the amount of actual grinding of each ground surface and the intended amount of grinding thereof varies from one suture needle to another, there occur variations in the penetrating ability. For controlling the grinding amount so as to form the foremost end of the suture needle into a pointed shape, the narrower the suture needle is, the higher precision is required, and the cost is increased.
Referring to other prior art, Japanese Patent Publication No. 57337/85 discloses a suture needle having a distal end portion pressed into a flattened configuration, and first, second and third ground surfaces are formed at this distal end portion, the second and third ground surfaces intersecting the first ground surface at an acute angle to form cutting edges. The cross-sectional area of the distal end portion of the suture needle is decreasing progressively toward the distal end thereof. The second and third ground surfaces do not intersect each other at that portion of the suture needle remote from the distal end thereof, and therefore this portion has a trapezoidal cross-section. The second and third ground surfaces intersect each other at that portion of the suture needle near the distal end thereof, and therefore this portion has a triangular cross-section. Further, an auxiliary ground surface is formed at the distal end portion of the suture needle, and this auxiliary ground surface intersects the second and third ground surfaces to make the foremost end pointed. The auxiliary ground surface serves to make the foremost point less sharp.
U.S. Pat. No. 4,128,351 discloses a suture needle in which a distal end portion of the suture needle is formed into a triangular cross-section by three ground surfaces. The angle between one ground surface and the axis of the distal end portion is greater than the angle of each of the other two ground surfaces and the axis of the distal end portion.
Japanese Utility Model Publication No. 6885/86 discloses a technique by which the grinding is carried out along a pair of cutting edges of a suture needle of a triangular cross-section, thereby forming another pair of cutting edges.